Power injectors for injecting fluid into animals are well known in the art. A typical power injector comprises an injector head, having a syringe mount, and a drive ram reciprocally mounted thereon. This syringe is mounted to the injector in either a breach-load manner or a front load manner. The syringe can either be pre-filled or empty, i.e., the user must first draw contrast into the syringe before injecting fluid.
Syringes for power injectors are also well known in the art. As stated in the preceding paragraph, the syringe can be a front load type, in which the rear end of the syringe is inserted into the injector to attach the syringe to the injector. Additionally, the syringe could be breach loaded, such that, for example, a face plate of the injector is rotatable and the syringe is loaded through the rear the face plate, front end first.
A drive ram of the injector may attach to the plunger of the syringe to move the plunger forward relative to the syringe, to expel fluid from the discharge end of the syringe. In typical injection procedures, the pressure generated by the forward translation of the plunger can range from about 100 psi to 1200 psi. To ensure that contrast fluid from the syringe does not leak past the plunger, plunger assemblies typically comprise at least two (2) integral sealing rings that contact the inside surface of a syringe barrel. Typically, the forward-most sealing ring performs the majority of the sealing process, and the rearward most sealing ring is a backup safety seal in case the forward-most ring fails.
One aspect of syringe plungers having two (2) seal sealing rings relates to sterilization of the area between the two (2) sealing rings, once installed in the syringe. With most materials, it is difficult for a sterilization gas to reach the area between the two (2) sealing rings. Accordingly, there is a need for a syringe jacket (seal) that overcomes the deficiencies in the prior art. The embodiments of the present invention overcome the difficult-to-sterilize space between the two seals when the plunger is installed in the syringe.
Another aspect of syringe plungers relates to how the plunger jacket moves against the interior surface of the syringe barrel during expulsion of fluid from the syringe. Some materials, from which the plunger jacket is constructed, have greater tactile resistance than other materials. When driven forward through the barrel, plunger jackets made from such materials may chatter or intermittently stick to the side walls, which may introduce noise into CT scanning systems utilizing the power injector and syringe. While other materials may glide easier against the surface of the barrel, such materials may not have sufficient tensile strength to maintain a seal against certain pressures during use. What is needed is a plunger that smoothly and evenly travels down the barrel without chatter but also seals against the operating pressures of the syringe. The embodiments of the present invention obviate the aforementioned problems.